Heat indicator of the pyrometerthermocouple type



Oct. 18, 1955 w. s. SAWLE, JR

HEAT INDICATOR OF THE PYROMETER-THERMOCOUPLE TYPE 2 Sheets-Sheet l INVENTOR.

Filed Dec. 5, 1951 Oct. 18, 1955 w. s. SAWLE, JR 2,720,786

HEAT INDICATOR OF THE PYROMETER-THERMOCOUPLE TYPE Filed Dec. 5, 1951 2 Sheets-Sheet 2 MW U T 0 0 1; O W WW 6 fi XV it: 97% L A Q m i Q X I Q, 5% Q N N l\ i 3 E3 l {Q IN V EN TOR.

nited 2,720,786 Patented Oct. 18, 1955 HEAT INDICATOR OF THE PYROIVIETER- THERMOCOUPLE TYPE William S. Sawle, Jr., Kenilworth, Ill. Application December 5, 1951, Serial No. 259,960

1 Claim. (Cl. 73-359) The present invention relates generally to heat indicators. More particularly the invention relates to that type of heat indicator which is designed primarily for use in connection with a die casting machine, serves as a medium or instrumentality for accurately indicating the temperature of the molten metal in the pot of the machine and comprises in addition to a pyrometer a thermocouple in the form of at protecting tube with one end portion thereof closed and positioned in the body of molten metal in the pot, and a pair of wire-like elements which are formed of dissimilar metal substances, have certain ends thereof disposed within the protecting tube and twisted or otherwise connected together, have their remaining portions spaced apart by insulators, have the other ends thereof connected to the binding posts of the pyrometer and operate when the ends thereof within the protecting tube are subjected to heat, to generate such electric current as to actuate the pyrometer for temperature indicating purposes.

A heat indicator of the aforementioned type is an extremely important adjunct of the die casting machine because it is essential that the molten metal in the pot be maintained within a predetermined range of temperature. If the metal becomes too cool it partially solidifies and cannot be forced by the plunger of the machine into the mold cavity. If the metal becomes too hot its physical properties are changed to such an extent that the die castings that are formed by the machine are imperfect because of brittleness and porosity. In a heat indicator of the type heretofore mentioned it is standard practice to form the protecting tube of cast iron or porcelain. If the tube is formed of cast iron it quickly corrodes due to heat and oxidation. If the tube is formed of porcelain it is so fragile that it often breaks. In the event of corrosion or breakage of the tube short circuiting occurs with the result that the heat indicator as a whole becomes inoperative and it is necessary to replace the thermocouple at a comparatively high cost while the die casting machine stands idle.

The primary object of the invention is to provide a heat indicator of the type under consideration which is an improvement upon, and eliminates the objections to, conventional indicators for die casting machines and is characterized by the fact that the protecting tube thereof, instead of being formed of plain cast iron or porcelain, is formed of nitrified cast iron. By forming the tube of nitrified cast iron the protecting tube while in the body of molten metal in the pot of the die casting machine with which the indicator is used, is subjected to substantially no corrosion due to oxidation and heat and hence the indicator as a whole possesses extremely long life and requires but infrequent replacement of the thermocouple part thereof.

Another object of the invention is to provide a heat indicator which is generally of new and improved construction and effectively and efficiently fulfills its intended purpose.

Other objects of the invention and the various advantages and characteristics of the present heat indicator will be apparent from a consideration of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by the claim at the conclusion hereof.

In the drawings which accompany and form a part of this specification or disclosure and in which like numerals of reference denote corresponding parts throughout the several views:

Figure 1 is a fragmentary side view of a die casting machine having associated therewith a heat indicator embodying the invention;

Figure 2 is a plan view illustrating in detail the manner in which the thermocouple of the heat indicator is supported so that the nitrified cast iron protecting tube is disposed in the body of molten metal in the pot of the machine; and

Figure 3 is a longitudinal section of the so-called hot leg of the thermocouple.

The heat indicator that is shown in the drawings con? stitutes the preferred form or embodiment of theinven-v tion. It forms, in effect, a part of a conventional die casting machine and serves, as described in detail hereafter, accurately to indicate the temperature of the molten metal which is used in the machine to form die castings, As shown in Figures 1 and 2 of the drawings, the-die casting machine comprises a supporting structure 4 a die clamping arrangement 5, a pot 6 and a cylinder and piston device 7. The supporting structure 4 is adapted to rest on the floor of the establishment in which the die casting machine is used. The die clamping arrangement 5 is disposed over the upper portion of the supporting structure 4 and comprises a plurality of vertically extending laterally spaced posts 8, a fixed or stationary clamp mem. her 9 and a vertically movable clamp member 10. The posts are illustrated as being four in number and are arranged in a rectangular pattern. The lower ends of the posts are suitably connected to th upper portion of the supporting structure 4 and the upper ends of the posts are connected to the corners of a rectangular horizontally extending plate 11. The clamp member 9 is fixedly mounted on the lower ends of the posts 8, extends horizontally and is adapted to hold or retain the lower part of a two-part die(not shown). The clamp member 16) is mounted on the posts to slide upwards and downwards between the clamp member 9 and the plate 11 and carries the upper part of the aforementioned die. When the clamp member 10 is slid downwards the upper part of the die is brought into clamped relation with the lower die part and the die, as well understood in the art, is thus readied to receive a charge of molten metal for casting forming purposes. When the clamp member 10 is shifted or slid upwards the upper part of the die is raised with respect to the fixed lower die part and hence exposes the casting so that it may be removed. The pot 6 of the die casting machine is horizontally elongated and has one end portion thereof disposed under the clamp member 9 and suitably secured to the upper portion of the supporting structure 4. The other end portion of the pot is disposed at one side of the upper portion of the supporting structure and has the top thereof open. The pot is adapted to hold a body of molten die casting metal (aluminum, zinc, or other white metal alloy) and has associated with it burner means 12 for maintaining the body of metal in the pot in a molten condition. The cylinder and piston device 7 of the die casting machine is located outwards and upwards of said other end portion of the pot 6 and consists of a cylinder 13 and a slidably mounted piston 14 in the cylinder. The cylinder:

13 is supported in a fixed position by way of a pair of laterally spaced upwardly inclined arms 15, the upper ends of which are suitably connected to the cylinder and the lower ends of which are bolted or otherwise fixedly secured to the exposed end portion of the pot 6. The piston 14 is provided with a rod 16 which extends through one of the end walls of the cylinder and is operatively connected to a plunger (not shown) by way of a linkage 17. When the piston 14 is slid to the right, as viewed in Figures 1 and 2, it operates through the medium of the linkage 17 so to control the plunger as to cause the latter to force molten metal from the pot 6 into the cavity in the die. When the piston is shifted in the opposite direction the plunger is retracted.

As its principal components or parts the heat indicator comprises a pyrometer 18 and a thermocouple. The purpose of the heat indicator is to show or register the temperature of the molten metal in the pot 6 to the end that the operator of the die casting machine will be able by control of the burner means 12 to maintain the body of molten metal within the proper temperature range.

The pyrometer 18 is of standard or conventional construction and is suitably supported at any desired location within convenient visual range of the pot of the die casting machine. It comprises a window equipped casing 19, a calibrated rotor 20 within the casing and a pointer 21 adjacent the window of the casing, and operates in response to variatlons in electric current. In connection with supply of current to the pyrometer the calibrated rotor 20 turns or revolves so that the markings or calibrations thereon coact with the pointer to indicate various degrees of temperature to which the thermocouple is subjected.

The thermocouple of the heat indicator comprises an inverted V-shaped pipe 22, a protecting tube 23, and a pair of wire-like elements 24 and 25, and is in juxtaposition with the exposed end portion of the pot 6 of the die casting machine. The V-shaped pipe 22 comprises a pipe section 26, an elbow 27 and a pipe section 28. The pipe section 26 is inclined downwards in the direction of the body of molten metal in the pot. The pipe section 28 is downwardly inclined in the opposite direction and has its upper end connected to the upper end of the pipe section 26 by the elbow 27. A bracket 29 serves to support the inverted V-shaped pipe 22 in its operative position. Such bracket is connected to one of the arms 15 and has a set screw equipped sleeve 30 through which extends the upper end of the pipe section 28. The protecting tube 23 of the thermocouple constitutes the essence of the invention and is located at, and connected to, the lower end of the pipe section 26 of the inverted V-shaped pipe 22. of a cylindrical side wall 31 and an end wall 32 at one end of the side wall. As shown in the drawings, the inverted V-shaped pipe 22 is so supported by the bracket 29 that the protecting tube 23 is disposed for the most part within the body of molten metal in the pot 6. The protecting tube forms, in effect, a lower continuation of the pipe section 26 and is connected to the latter by a screw thread connection 33 between the open or free marginal portion of the tube side wall and the lower end of said pipe section 26. It is nitrified by placing it in a tightly sealed retort and introducing into the retort for a period of approximately 72 hours disassociated ammonia at a temperature of 980 F. or above. In connection with the nitrifying process the ammonia breaks up into hydrogen and nitrogen and the nitrogen combines with the cast iron to form hard iron nitrides. After the nitrifying process the exposed surfaces of the protecting tube 23 are nitrified to a depth between and A of an inch and the nitrified portions have a hardness of 94 minimum Rockwell 15 N. Preferably the side and end walls 31 and 32 of the protecting tube are approximately A; of an inch thick. After the nitrifying operation the outer surfaces of the side and end walls are machined and then treated with emery or other abrasive material so that they are polished to such an extent that It is formed of nitrified cast iron and consists r the molten die casting metal in the pot of he die casting machine will not adhere to them. By nitrifying the protecting tube which is immersed or disposed within the body of molten die casting metal in the pot the tube is so protected against corrosion from heat and oxidation that it has extremely long life. The wire-like elements 24 and 25 of the thermocouple extend longitudinally through the inverted V-shaped pipe 22 and have certain ends thereof disposed Within the protecting tube 23, as shown in Figure 3 of the drawings. They are formed of dissimilar metal substances, such, for example, as iron and constantan, and when subjected to the heat of the molten metal in the pot 6 generate an electric current. The extremities of the elements that are disposed within the protecting tube 23 are twisted together and united by welding. The oher portions of the elements are spaced apart by way of a series of cylindrical porcelain insulators 34. The latter have spaced apart longitudinally extending holes through which extend such portions of the wire-like elements 24 and 25. The separated ends of the elements that are located in the lower end of the pipe section 28 of the inverted V-shaped pipe 22 are connected to certain ends of the leads of a two-lead flexible conductor 35. 'The other ends of the leads of the conductor are connected to binding posts (not shown) on the pyrometer casing 19.

The herein described heat indicator effectively and etficiently fulfills its intended purpose and, due to the fact that it includes the nitrified protecting tube on the hot leg of the thermocouple, possesses extremely long life.

Whereas the heat indicator has been described in connection with a die casting machine it is to be understood that it has other capabilities of use. It is also to be understood that the invention is not to be restricted to the details set forth since these may be modified within the scope of the appended claim without departing from the spirit and scope of the invention.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

In combination with a die casting machine having a pot for a body of die casting metal of the white metal alloy type together with heating means for maintaining the body in a molten condition, a heat indicator adapted to indicate the temperature of the molten metal in the pot and comprising a pyrometer disposed exteriorly of the pot, an elongated protecting tube formed of cast iron, consisting of a continuous side wall and an end wall at one end of the side wall, having its side and end walls approximately one-eighth of an inch in thickness, having all surfaces of its side and end walls nitrified to a depth between 2 one hundredths and 3 one hundredths of an inch and a hardness of approximately 94 minimum Rockwell 15 N in order that the tube as a whole is substantially immune to corrosion from heat and oxidation and provided with mounting means therefor whereby it is positioned so that its end portion with the end wall is immersed in the body of metal in the pot, and a pair of juxtapositioned wire-like elements formed of dissimilar metal substances, having certain ends thereof extending into the interior of the protecting tube through the other end of the side wall and connected together, having their remaining portions spaced apart and having the other ends thereof connected electrically to said pyrometer.

References Cited in the file of this patent UNITED STATES PATENTS Mar. 21,1919

OTHER REFERENCES A. S. S. T. Nitriding Symposium, October 1929, p. 222. 

